A bargraph display is an instrumentation indicator which has distinct advantages over digital and mechanical analog panel meters in many applications. As an analog meter the bargraph is easy to quickly and accurately interpret and to scan for trend or comparison information.
Electronic bargraphs presently on the market include light emitting diode (LED) displays, incandescent displays, liquid crystal displays, and gas discharge displays. Each of these bargraphs has its own advantages and disadvantages, which deal mainly with power consumption, operating environment considerations, brightness, ease of interfacing with electronic drive circuitry. Most such devices suffer from relatively small display areas and from inability to operate in a wide range of environmental conditions.
The use of electroluminescent flat panel displays integrated with thin-film transistor control circuitry is taught by U.S. Pat. No. 4,006,383. Such devices are particularly useful for displaying alpha-numeric information. The electroluminescent (EL) display element is made part of a relatively simple thin-film transistor control circuit which is associated with each individual display element.
It is desirable to design and fabricate an electronic bargraph which is capable of an analog display appearance and high resolution. The display medium should have rapid response, high brightness, be environmentally rugged, and easily integrated with the electronic drive circuitry. The electronic drive circuitry should be integratable with the display elements and give reliable and flexible operating capability to the system.